
import {
	Blob,
	btoa,
	createImageBitmap,
	CSSStyleDeclaration,
	performance,
	document,
	DOMParser,
	EventTarget,
	fetch,
	Headers,
	HTMLCanvasElement,
	Image,
	HTMLImageElement,
	ImageBitmap,
	location,
	navigator,
	Request,
	requestAnimationFrame,
	cancelAnimationFrame,
	Response,
	URL,
	window,
	self,
	WebAssembly,
	Worker,
	XMLHttpRequest,
	ImageData,
	TextDecoder,
	core
	} from 'dhtml-weixin';
import { tslFn } from '../../shadernode/ShaderNode.js';

// Microfacet Models for Refraction through Rough Surfaces - equation (33)
// http://graphicrants.blogspot.com/2013/08/specular-brdf-reference.html
// alpha is "roughness squared" in Disney’s reparameterization
const D_GGX = tslFn( ( { alpha, dotNH } ) => {

	const a2 = alpha.pow2();

	const denom = dotNH.pow2().mul( a2.oneMinus() ).oneMinus(); // avoid alpha = 0 with dotNH = 1

	return a2.div( denom.pow2() ).mul( 1 / Math.PI );

} ).setLayout( {
	name: 'D_GGX',
	type: 'float',
	inputs: [
		{ name: 'alpha', type: 'float' },
		{ name: 'dotNH', type: 'float' }
	]
} ); // validated

export default D_GGX;
